The reading of electrical energy, water flow, and gas usage has historically been accomplished with human meter readers who came on-site and manually documented meter readings. Over time, this manual meter reading methodology has been enhanced with walk by or drive by reading systems that use radio communications to and from a mobile collector device in a vehicle. Recently, there has been a concerted effort to accomplish meter reading using fixed communication networks that allow data to flow from the meter to a host computer system without human intervention.
Fixed communication networks can operate using wire line or radio technology. For example, distribution line carrier systems are wire-based and use the utility lines themselves for communications. Radio technology has tended to be preferred due to higher data rates and independence from the distribution network. Radio technology in the 902-928 MHz frequency range can operate without an FCC license by restricting power output and by spreading the transmitted energy over a large portion of the available bandwidth.
Automated systems, such as Automatic Meter Reading (AMR) and Advanced Metering Infrastructure (AMI) systems, exist for collecting data from meters that measure usage of resources, such as gas, water and electricity. Such systems may employ a number of different infrastructures for collecting this meter data from the meters. For example, some automated systems obtain data from the meters using a fixed wireless network that includes, for example, a central node, e.g., a collection device, in communication with a number of endpoint nodes (e.g., meter reading devices (MRDs) connected to meters). At the endpoint nodes, the wireless communications circuitry may be incorporated into the meters themselves, such that each endpoint node in the wireless network comprises a meter connected to an MRD that has wireless communication circuitry that enables the MRD to transmit the meter data of the meter to which it is connected. The wireless communication circuitry may include a transponder that is uniquely identified by a transponder serial number. The endpoint nodes may either transmit their meter data directly to the central node, or indirectly though one or more intermediate bi-directional nodes which serve as repeaters for the meter data of the transmitting node.
Some networks may employ a mesh networking architecture. In such networks, known as “mesh networks,” endpoint nodes are connected to one another through wireless communication links such that each endpoint node has a wireless communication path to the central node. One characteristic of mesh networks is that the component nodes can all connect to one another via one or more “hops.” Due to this characteristic, mesh networks can continue to operate even if a node or a connection breaks down. Accordingly, mesh networks are self-configuring and self-healing, significantly reducing installation and maintenance efforts.
Communication systems have existed for many years, but upgrades to a given system typically require replacement or upgrade of devices to support the capabilities of a new system. Specifically, a given upgrade may increase the data rate used for communications. Typically, data rate increases result in compatibility issues between existing or legacy devices and the new, more capable equipment. A second factor in wireless communications is the relationship between communication data rates and communication performance. As a rule of thumb, the receiver sensitivity of a device is degraded by 3 dB each time the data rate is doubled.
Some existing Local Area Network (LAN) systems may use frequency hopping spread spectrum (FHSS) communications. Some existing systems may allow for per-message synchronization between devices, where a receiving device synchronizes to a transmitting device by prioritizing channels based on the received signal strength (RSSI), and then detecting a valid preamble on the prioritized channel list. Some existing systems may also be predominantly a two-way system, where the system collector requests, or polls, data from end devices. The preamble duration may allow a receiving device to scan all frequency hopping channels and rank the received signal strength (RSSI) for the highest channels. The process may be repeated a number of times before the receiving device selects the strongest RSSI channel to check for a valid preamble.
Accordingly, a need exists for a technique for maintaining compatibility between newer equipment and legacy equipment or services that are capable of communicating at different data rates.